Battery driven ground power unit with improved construction, operability, durability and maintenance

ABSTRACT

An airport ground power unit for supplying electric current to an aircraft parked on the ground, a method of operating the ground power unit, a system for supplying electric current to an aircraft parked on the ground, a method of operating such system, and a Y-adaptor.

CROSS REFERENCE TO RELATED APPLICATION

This application is a National Phase filing in the United States, under35 USC § 371, of PCT International Patent Application PCT/US2019/023542,filed on 22 Mar. 2019 which claims the priority of PCT InternationalPatent Application PCT/US/2018/054668, filed 5 Oct. 2018; which claimsthe priority of European Patent Application EP 17195353.2, filed 7 Oct.2017.

This application is also a continuation-in-part of U.S. patentapplication Ser. No. 16/649,066, filed 19 Mar. 2020, which is a 371filing of PCT/US2018/054668, filed 5 Oct. 2018; which claims thepriority of European Patent Application EP 17195353.2, filed 7 Oct.2017.

These co-pending applications are hereby incorporated by referenceherein in their entirety and is made a part hereof, including but notlimited to those portions which specifically appear hereinafter.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to systems for supplying electric current to anaircraft parked on the ground, comprising a battery aircraft groundpower unit (GPU).

Discussion of Related Art

In the related art “Referenzbericht: eGPU Energieversorgung vonFlugzeugen” by ARADEX AG, CH, a battery driven ground power unit ispresented.

The inventors wanted to improve construction, operability, durabilityand maintenance of such battery driven GPU. The object of the inventiontherefore was to provide a GPU with improved construction, operability,durability and/or maintenance.

In this application the term battery GPU generally relates to a GPUcomprising one or more batteries. It may in addition be a hybrid GPU,containing in addition a combustion engine and generator.

SUMMARY OF THE INVENTION

The object of improving operability of a battery GPU is achieved by asystem for supplying electric current to an aircraft parked on theground, comprising a battery GPU for supplying electric current to anaircraft parked on the ground, preferably according to any of the hereindescribed battery GPU embodiments, the battery GPU comprising one ormore batteries, and an inverter for transforming an output current ofthe one or more batteries to an alternating output current of theinverter to be supplied to the aircraft, wherein the battery GPUcomprises an alternating current input port, wherein the battery GPU isconfigured to be connected to an alternating current output connector ofa helper GPU via the alternating current input port, in order to routean alternating output current of the helper GPU via the alternatingcurrent input port to the aircraft.

It is also achieved by a method of operating a system for supplyingelectric current to an aircraft parked on the ground, preferably asystem according to the invention, comprising a battery GPU forsupplying electric current to an aircraft parked on the ground,preferably according to any of the herein described battery GPUembodiments, by using one or more batteries, preferably using a GPUoperation method according to any of the herein described GPU operationmethods, and the system further comprising at helper GPU for supplyingelectric current to an aircraft parked on the ground, wherein the methodcomprises the steps:

-   connecting a helper GPU's alternating current output connector to an    alternating current input port of the battery GPU, and routing an    alternating output current of the helper GPU to the aircraft via the    alternating current input port.

Hereby, duration of continuous use of a battery GPU can be extended byperforming a handover of aircraft power supply from the battery orbatteries of the battery GPU to the respective power source (e.g.,battery or generator) of the helper GPU.

In a further preferred system according to the present invention, thealternating current input port comprises an aircraft socket, beingconfigured to be connected to an aircraft output connector adapted to beconnected to the aircraft.

Hereby the GPUs can be connected to each other with the existing GPUaircraft output connector. Conventional (e.g., Diesel) GPUs can beeasily used as helper GPU.

The aircraft socket is a socket of the type that is integrated in thebody of an airplane, to which the GPU's aircraft output connector isconnected for powering the aircraft. It is standardized (6 pole, 400 Hz)and known to the one skilled in the art.

The aircraft socket is preferably embedded in the housing of the GPU.Alternatively, the output cable of the GPU features the aircraft socketby way of a Y-cable configuration.

In a further preferred system according to the present invention, thebattery GPU comprises a Y-adaptor which has two alternating currentinput ports each comprising an aircraft socket, and which has anaircraft output connector, whereby an aircraft output connector of thebattery GPU is connected to one of the two alternating current inputports. Preferably the Y-adaptor comprises the input coupling switch foreach phase to be switched (e.g., 4 phases).

Hereby a battery GPU can be easily equipped with an alternating currentinput port.

In a further preferred system according to the present invention, thesystem is configured to synchronize to each other

-   the alternating output current of the inverter of the battery GPU,    preferably a phase angle and/or a frequency and/or a amplitude of    the output, and-   the alternating output current of the helper GPU, preferably a phase    angle and/or a frequency and/or a amplitude of the output.

Hereby, smooth handover of power delivery between the GPUs can beprepared. It is preferred to synchronize phase angle and frequency andamplitude. However, in practice the parameter having the highest impacton a smooth transfer might be the phase angle as amplitude and frequencymight be controlled by each GPU to a sufficiently exact degree, whilethe phase angle between the currents of the two GPU is initiallyuncorrelated. Therefore, synchronizing only the phase angle of theoutput currents might already be enough for a smooth handover.

In a further preferred system according to the present invention, thesystem, preferably the battery GPU, comprises an input coupling switch,and whereby the system, preferably battery GPU, is configured

-   to detect a parameter (e.g., the phase angle or frequency or    amplitude—preferably phase angle) of the alternating output current    of the helper GPU and-   to close the input coupling switch, if the difference between the    detected parameter and a respective parameter of the alternating    output current of the inverter of the battery GPU is smaller or    equal to a predetermined threshold.

Hereby, smooth handover of power delivery between the GPUs is achieved.The step of detecting may be performed as part of the synchronization.

In a further preferred system according to the present invention, thesystem, preferably the battery GPU, is configured to shift a parameter(e.g., the phase angle or frequency or amplitude—preferably phase angle)of the alternating output current of the inverter of the battery GPUand/or, for example via a communication channel to the helper GPU'scontroller or inverter, to shift a parameter (e.g., the phase angle orfrequency or amplitude—preferably phase angle) of the alternating outputcurrent of the helper GPU.

Hereby, the synchronization of the GPUs' output currents can beaccelerated by actively shifting one or more parameters of the outputcurrents.

In a further preferred system according to the present invention, thesystem, preferably the battery GPU, comprises an output decouplingswitch, and whereby the system, preferably the battery GPU, isconfigured

-   to open the output decoupling switch, if the input coupling switch    has been switched to closed state.

Hereby, the battery GPU's inverter is disconnected or deactivated suchthat correct power delivery avoiding unbalanced power draw from thebattery GPU and the helper GPU is achieved. Preferably, the outputdecoupling switch is switched within seconds or milliseconds after theinput coupling switch has been switched to closed state. Preferably, thedecoupling switch can be one of the switches of the inverter fordeactivating the inverter.

In a further preferred system according to the present invention, thesystem further comprises the helper GPU, whereby the battery GPU and thehelper GPU are connected to each other via the alternating current inputport at the battery GPU and the alternating current output connector ofthe helper GPU.

In a further preferred system according to the present invention, fortransforming the output current of the one or more batteries to thealternating output current of the inverter, the one or more batteriesare connected to an input port of the inverter, and the system isconfigured to route the alternating output current of the helper groundpower unit from the alternating current input port via the input port ofthe inverter to the aircraft, whereby the system comprises an inputconverter which is configured to convert the alternating output currentof the helper ground power unit at the alternating current input port toa directed current and to output the directed current to the input portof the inverter.

Hereby, it is possible to feed the electric power of the helper CPU intothe DC-bus of the battery GPU. The advantage of this topology is that asno-break-power-transfer can be achieved without synchronization or timedswitching of the helper GPU; it however requires the input converter asan additional component. It is possible to start the helper GPU at anytime as the helper GPU first takes over the power when the DC-voltageout of the batteries goes below the output voltage of the inputconverter. Hence, the helper GPU just takes over the load when connectedand the battery voltage gets below the rectifier voltage. Additionally,the batteries will take over the load again in case the helper GPU failsand stops delivering power to the inverter. Preferably, the inputconverter is configured to provide a converted output voltage ofapproximately 15% to 25%, more preferred 20%, of the maximum batterycharge and/or approximately 325V dc.

In a further preferred system according to the present invention, theinput converter comprises one or more of: transformer, rectifier,filter, filter diode, choke. The transformer rectifier configuration canbe of any type, provided the resulting ripple voltage is below a certainpredetermined level.

In a further preferred method according to the present inventionregarding operating a system, the connecting further comprises one ormore of the following steps a)-c);

-   a) synchronizing to each other, preferably by shifting a parameter    (e.g., phase angle, frequency, amplitude) of the alternating output    current of the inverter of the battery GPU and/or, for example via a    communication channel to the helper GPU's controller, by shifting a    parameter (e.g., phase angle, frequency, amplitude) of the    alternating output current of the helper GPU:-   the alternating output current of the inverter of the battery GPU,    preferably a phase angle and/or a frequency and/or an amplitude of    the output current, and-   the alternating output current of the helper GPU, preferably a phase    angle and/or a frequency and/or an amplitude of the output current;-   b) detecting a parameter (e.g., phase angle, frequency, amplitude)    of the alternating output current of the helper GPU and closing an    input coupling switch, if the difference between the detected    parameter and a respective parameter of the alternating output    current of the inverter of the battery GPU is smaller or equal to a    predetermined threshold; and preferably-   c) opening an output decoupling switch, if the input coupling switch    has been switched to closed state.

Preferably, the battery GPU is configured to perform phaseangle/frequency/amplitude detection, synchronization, shifting andswitching of the respective switches; and the respective hardware ispreferably implemented in the battery GPU. In that way, the helper GPUcan be a conventional GPU without additional intelligence for thispurpose. However, the scope of the invention also covers solutions wheresuch tasks are (all or only partially) performed by the helper GPU orshared between helper GPU and battery GPU. Helper GPU and battery GPUmay therefor communicate via communication channels in order to allowfor the desired operation.

In a further preferred method according to the present inventionregarding operating a system, the alternating output current of thehelper ground power unit is routed from the alternating current inputport via an input port of the inverter to the aircraft. Hereby, theactivation/deactivation of power transfer from the helper GPU can bedone easier, without specific synchronization, automatically based onthe power need. Preferably, the alternating output current of the helperground power unit is thereby converted to a dc current by an inputconverter of the battery GPU.

The object of improving operability of a battery GPU is furthermoreachieved by an Y-adaptor which has two alternating current input portseach comprising an aircraft socket, and which has an aircraft outputconnector.

Hereby a battery GPU can be easily equipped with an alternating currentinput port.

A system according to the invention preferably comprises a firstembodiment of an airport battery GPU, preferably mobile on wheels, forsupplying electric current to an aircraft parked on the ground, the GPUcomprising;

-   a first electric battery,-   an inverter for transforming an output current of the battery to an    alternating output current of the inverter to be supplied to the    aircraft,-   one or more first electronic switches for connecting and    disconnecting the first battery to and from the inverter, wherein    the one or more first switches is or are connected in serial to the    first battery and wherein the serially connected first battery and    the one or more first switches are together connected to the    inverter,-   a first controller unit for controlling at least one, preferably    all, of the one or more first switches;-   a second electric battery and-   one or more second electronic switches for connecting and    disconnecting the second battery to and from the inverter, wherein    the one or more second switches is or are connected in serial to the    second battery and wherein the serially connected second battery and    the one or more second switches are together connected to the    inverter such that they are in parallel to the serially connected    first battery and the one or more first switches, wherein at least    one, preferably all, of the one or more second switches is    controlled by the first digital controller unit or by a second    digital controller unit.

In addition to the one or more first switches being connected in serialto the first battery, a first diode is connected in serial, allowingcurrent from the first battery to the inverter and blocking or limitingcurrent from the inverter or the second battery to the first battery;and wherein in addition to the one or more second switches beingconnected in serial to the second battery, a second diode is connectedin serial, allowing current from the second battery to the inverter andblocking or limiting current from the inverter or the first battery tothe second battery.

A method of operating a system according to the invention preferablycomprises a first method of operating a GPU in order to supply currentto an aircraft parked on the ground the GPU comprising the steps:

-   by a first digital controller unit, switching one or more first    electronic switches for connecting and disconnecting a first battery    of the GPU to and from an inverter of the GPU,-   transforming an output current of the first battery to an    alternating output current of the inverter,-   by the first controller unit or by a second controller unit,    switching one or more second electronic switches for connecting and    disconnecting a second battery of the GPU to and from the inverter,-   by a first diode of the GPU, allowing current from the first battery    to the inverter and blocking or limiting current from the inverter    or the second battery to the first battery,-   by a second diode of the GPU, allowing current from the second    battery to the inverter and blocking or limiting current from the    inverter or the first battery to the second battery,-   transforming an output current of the second battery to the    alternating output current of the inverter.

Hereby, construction, operability, durability and maintenance of thebattery GPU are improved. For example, if one battery is disconnected,for some reason, during load, the remaining battery (or batteries, seebelow) can remain unaffected. Fully charged batteries can be on hold asa reserve connected to the inverter during an aircraft turnaround ifneeded. The diodes thereby prevent reverse charging or reverse chargingwith unlimited current, which would be harmful to the battery and/orlead to reduced efficiency.

Preferably, in that same manner, the GPU comprises a third battery withone or more third switches and third diode and/or a fourth battery withone or more fourth switches and fourth diode and/or further batterieswith one or more further switches and further diodes connected inparallel to the first and second battery and respective switches.Features that in the following are described as preferred for the firstand second battery scenario, preferably also apply, in case of more thantwo batteries, to the third, fourth or further battery scenariosaccordingly.

The first battery and second battery are preferably each configured tosustain 90 kW at the GPU's output port, loading to the airplane.Preferably, the first battery and second battery are built in the sameway having the same electrical specifications. The first battery and/orsecond battery are preferably battery packs, each built from multiplebattery cells.

The inverter is preferably configured to output 400 Hz ac, preferably3×200 Vac (phase-to-phase) @ 400 Hz, preferably at at least 90 kVA.

The first/second diode is at least (configured for) limiting the currentfrom the inverter or front the second/first battery to the first/secondbattery, e.g. by forcing any reverse current via a first/second shuntresistor, which could be a classic quasi-linear resistor or anothercurrent limiting element or current limiting circuit of elements.Particularly preferably, the first/second diode is (configured for)completely limiting the current from the inverter or from thesecond/first battery to the first/second battery, e.g. realized in thatno reverse current permitting shunt path exists parallel to therespective diode.

Preferably, the GPU does not comprise a combustion engine drivengenerator set with a continuous electric power output higher than 50%,preferably 30%, of the output power rating of the GPU.

Preferably, one or more, of the first switches and the first diode arerealized in one element, e.g. a transistor (preferably IGBT) orthyristor. The same is preferred for the second switches and secondfirst diode.

Preferably, one or more of the first switches and the first diode arerealized by an electronic relay (electro-mechanic or solid-state) and,if not the relay is already unidirectional, a separate, seriallyconnected diode. The same is preferred for the second switches andsecond first diode. Preferably, at least one of the one or more firstswitches and at least one of the one or more second switches is realizedas an electro-mechanic relay.

The output current of the battery could be led directly or indirectly(e.g. over a filter or another intermediate element) to the inverter.

Preferably, each battery has a battery monitoring device dedicated to itand the GPU is configured to disconnect any of the batteries by way ofopening one of the first or second switches in case the batterymonitoring device indicates a malfunction of the respective battery.

In a further preferred second embodiment of a GPU of a system accordingto the present invention, preferably based on the first GPU embodiment,the capacity of all batteries of the ground power in total is at least80 kWh.

Hereby, the battery is able to store sufficient energy to sustain acouple of aircraft turnarounds by only battery stored energy.

In a further preferred third embodiment of a GPU of a system accordingto the present invention, preferably based on any of the preceding GPUembodiments, at least one of the one or more first switches and at leastone of the one or more second switches are each configured to disconnectboth poles of the respective battery from the inverter. In a furtherpreferred method of operating a system according to the inventioncomprising a method of operating a GPU, preferably based on the first orany of the herein described GPU operation methods, both poles of therespective battery are connected to and disconnected from the inverter.

Hereby, safety of the GPU is improved. A complete disconnection of thebattery from the other electrical circuits can be advantageous inemergencies.

In a further preferred fourth embodiment of a GPU of a system accordingto the present invention, preferably based on any of the preceding GPUembodiments, the GPU comprises a battery charger configured to chargethe first battery and the second battery. In a further preferred methodof operating a system according to the in comprising a method ofoperating a GPU, preferably based on the first or any of the hereindescribed GPU operation methods, the first and second battery arecharged by the same charger, either at the same time or alternating.

Preferably, the GPU comprises a switch, preferably a 2-pole switch,

-   a) for connecting and disconnecting the charger to and from the    first/second battery-   b) or for connecting and disconnecting the charger to and from a    power source, inputting power to the charger.

Particularly, preferably in case a) this switch is one of the one ormore first/second switches.

In a further preferred fifth embodiment of a GPU of a system accordingto the present invention, preferably based on any of the first to thirdGPU embodiment, the GPU comprises a first battery charger configured tocharge the first battery and a second battery charger configured tocharge the second battery. In a further preferred method of operating asystem according to the invention comprising a method of operating aGPU, preferably based on the first or any of the herein GPU operationmethods, the first battery is charged by a first battery charger of theGPU and the second battery is charged by a second battery charger of theGPU.

Hereby, fast and easy charging is achieved. By the GPU comprising onecharger per battery, it is possible to charge the batteries from the50/60 Hz mains and in addition, the batteries can be charged in a fastmanner independently from each other. One charger per battery improvesutilization of the total battery capacity, i.e., when charging of abattery needs to “slow down” due to a high cell voltage, charging of theremaining packs can continue unaffected.

Preferably, the first controller is configured to control the firstcharger and the second controller is configured to control the secondcharger. Preferably, the chargers are connected to one common ordifferent connector of the GPU for connecting the charger to the gridpower.

Preferably, the GPU comprises,

-   a) a switch, preferably 2-pole, for connecting and disconnecting the    first charger to and from the first battery and a switch, preferably    2-pole, for connecting and disconnecting the second charger to and    from the second battery,-   b) or one or more switches for, together or separately, connecting    and disconnecting the first and second charger to and from a power    source, inputting power to the charger first and second charger.

Particularly, preferably in case a), the switches are ones of the one ormore first/second switches.

Hence, preferably, at least one of the one or more first switches isconfigured to disconnect the, preferably first, charger from the firstbattery, and at least one of the one or more second switches isconfigured to disconnect the, preferably second, charger from the secondbattery.

In a further preferred sixth embodiment of a GPU of a system accordingto the present invention, preferably based on any of the fourth to fifthGPU embodiment, the GPU comprises a combustion engine driven generatorset or a fuel cell with a continuous electric power output smaller orequal than 50%, preferably 30%, of the output power rating of the GPU,wherein the generator set is configured to feed the charger or the firstand/or second charger and/or configured to feed power directly into thecommon DC-bus (i.e., the batteries' output and/or the inverter's input)via a rectifier. In a thither preferred method of operating a systemaccording to the invention comprising a method of operating a GPU,preferably based on the first or any of the herein described GPUoperation methods, the charger or the fast and/or second charger is fedby an according generator set of the GPU.

Hereby a cost efficient and compact way of charging the batteries isprovided, by a very small engine or fuel cell, which would not bepowerful enough to sustain an aircraft for which the GPU is rated for,but powerful enough to charge the batteries up to a certain chargestatus.

In a further preferred seventh embodiment of a GPU of a system accordingto the present invention, preferably based on any of the fourth to sixthGPU embodiment, at least one of the one or more first switches isconfigured to disconnect the first battery from the inverter while

-   connecting the charger or the first battery charger to the first    battery-   and/or not disconnecting the charger or the first battery charger    from the first battery and wherein at least one of the one or more    second switches is configured to disconnect the second battery from    the inverter while;-   connecting the charger or the second battery charger to the second    battery-   and/or not disconnecting the charger or the second battery charger    from the second battery. In further preferred method of operating a    system according to the invention comprising a method of operating a    GPU, preferably based on the first or any of the herein described    GPU operation methods, switching the at least one of the one or more    first switches is disconnecting the first battery from the inverter    while connecting the charger or the first battery charger to the    first battery and/or not disconnecting the charger or the first    battery charger from the first battery and switching the at least    one of the one or more second switches is disconnecting the battery    from the inverter while connecting the charger or the second battery    charger to the second battery and/or not disconnecting the charger    or the second battery charger from the second battery.

Hereby, it is possible to charge the batteries while they are not beingdischarged.

In a further preferred eighth embodiment of a GPU of a system accordingto the present invention, preferably based on any of the preceding GPUembodiments, the one or more second switches are controlled by thesecond controller unit, wherein the GPU comprises a first batterymonitoring device for monitoring a correct function of the firstbattery, the first controller is connected to the first batterymonitoring device via a first communication line for communication withthe first battery monitoring device and configured to disconnect thefirst battery, preferably from the inverter and/or the charger, byopening at least one of the one or more first switches, as soon as thefirst battery monitoring device indicates a malfunction of the firstbattery, wherein the GPU comprises a second battery monitoring devicefor monitoring a correct function of the second battery, wherein thesecond controller is connected to the second battery monitoring devicevia a second communication line for communication with the secondbattery monitoring device and configured to disconnect the secondbattery, preferably from the inverter and/or the charger, by opening atleast one of the one or more second switches, as soon as the secondbattery monitoring device indicates a malfunction of the second battery.In further preferred method of operating a system according to theinvention comprising a method of operating a GPU, preferably based onthe first or any of the herein described GPU operation methods, thebatteries accordingly monitored and upon a malfunction the switches areaccordingly switched to disconnect the respective battery.

Hereby, safety of the GPU is improved, as each battery has its ownsafety shut-off system.

Preferably, the first and second battery monitoring devices are batterymanagement controllers configured to monitor one or more of thefollowing:

-   voltage: total voltage, voltages of individual cells, minimum and    maximum cell voltage or voltage of periodic taps;-   temperature: average temperature, coolant intake temperature,    coolant output temperature, or, temperatures of individual cells;-   state of charge (SOC) or depth of discharge (DOD), to indicate the    charge level of the battery;-   state of health (SOH), a variously-defined measurement of the    overall condition of the battery;-   coolant flow: for air or fluid cooled batteries;-   current: current in or out of the battery; and/or-   insulation resistance: isolation between battery pole and housing    and configured to indicate to the respective first and second    controller if any of the foregoing or a value computed of one of the    foregoing is out of its allowed boundaries to indicate a    malfunction.

Preferably, the first communication line is galvanically isolated fromthe second communication line. This further improves safety.

Preferably, the first and second controller each communicate to therespective battery monitoring device via a communication bus (e.g. CANbus).

In a further preferred ninth embodiment of a GPU of a system accordingto the present invention, preferably based on the eighth GPU embodiment,the GPU comprises a digital central controller, wherein the centralcontroller is connected to a user interface, and is configured to becontrolled by a user using user interface, and is connected to the firstcontroller and to the second controller via a communication bus. Infurther preferred method of operating a system according to theinvention comprising a method of operating a GPU, preferably based onthe first GPU or any of the herein described operation methods, the GPUis accordingly used by a user and the central controller accordinglycommunicates with the first and second controller.

Hereby, safety is further improved as the overall control of the GPU byuser is going through separate central controller, relieving the firstand second controller from these tasks.

The central controller is preferably configured to send switching to thefirst and second controller for connecting or disconnecting and/orcharging the first or second battery. The first controller and secondcontroller are configured to receive these commands and switch the oneor more first and second switches and or control the first and secondchargers accordingly. Preferably, the first controller and secondcontroller are configured to reject a command for connecting ordisconnecting and/or charging the first or the second battery in case ofa malfunction of the first or second battery, indicated by the first orsecond battery monitoring device.

The central controller is preferably configured to control the inverter.

Preferably, communication lines of the communication bus between thecentral controller and the first and second controller are galvanicallyinsulated from the first and second communication lines between thefirst and second controller and the first and second battery monitoringdevice.

In a further preferred tenth embodiment of a GPU of a system accordingto the present invention, preferably based on any of the preceding GPUembodiments, at least one of the one or more first switches and thefirst battery form a first battery module housed in a first housing, andwherein at least one of the one or more second switches and the secondbattery from a second battery module housed in a second housing.

Hereby, construction, maintenance and safety are further improved. Suchmodules can be easier put into the GPU and exchanged. Further, effect ofmalfunctions, e.g. fire, can be limited by the housing. The housing ispreferably fireproof, e.g. by being metallic. Preferably, the batterymonitoring device (see above) is also part of the so formed batterymodule.

In a further preferred eleventh embodiment of a GPU of a systemaccording to the present invention, preferably based on the tenth GPUembodiment, the first and second battery module each contain asoft-start device for temporarily limiting the output current of therespective first and second battery after connecting the respectivefirst and second battery is being connected to the inverter by means ofthe one or more first and second switches. In a further method ofoperating a system according to the invention comprising a method ofoperating a GPU, preferably based on the first or any of the hereindescribed GPU operation method, the output current of the respectivefirst and second battery is accordingly limited temporarily.

In a further preferred twelfth embodiment of a GPU of a system accordingto the present invention, preferably based on any of the preceding GPUembodiments, the GPU, preferably each of the first and second housing,comprises a heating device configured to be automatically switched on orsupplied with increased power, when the temperature falls below apredetermined temperature (e.g., −20° C.), and to be automaticallyswitched off or supplied with decreased power again, when thetemperature reaches a temperature above or equal to the predeterminedtemperature. In a further method of operating a system according to theinvention comprising a method of operating a GPU, preferably based onthe first or any of the herein described GPU operation methods, aheating element is accordingly switched/controlled.

In a further preferred thirteenth embodiment of a GPU of a systemaccording to the present invention, preferably based on any of thepreceding GPU embodiments, the GPU comprises an inductance connectedserially between the inverter and the first and second battery. In afurther method of operating a system according to the inventioncomprising a method of operating a GPU, preferably based on the first orany of the herein described GPU operation methods, current peaks to theinverter are damped by an inductance between inverter and the first andsecond battery.

Hereby, operability of the ground power system is further improved. Adisconnected battery can be reconnected, although it has a highervoltage than the remaining packs and in that case the inductance willlimit the inrush current into the inverter to an acceptable level. Someof the battery packs can be charged while others are used to sustain theload (discharged).

In a further preferred method of operating a system according to thepresent invention comprising a second method of operating a GPU,preferably based on the first or any of the herein described GPUoperation method, the switching of one or more first electronic switchesand the switching of the one or more second electronic switchescomprise:

-   switching at least one of the one or more first electronic switches    for connecting the first battery to the inverter;-   switching at least one of the one or more second electronic switches    for connecting the second battery to the inverter;-   switching at least one of the one or more first electronic switches    for disconnecting the first battery from the inverter, while    continuing to transform the output current of the second battery to    the alternating output current of the inverter, and then charging    the first battery by a battery charger of the GPU;-   after a certain time switching at least one of the one or more first    electronic switches for connecting again the first battery to the    inverter, in order to transform the output current of the now    recharged first battery to the alternating output current of the    inverter, while blocking or limiting current from the first battery    to the second battery by the second diode.

In a further preferred method of operating a system according to thepresent invention comprising a third method of operating a GPU based onthe first or any of the herein described GPU operation method, theswitching of the one or more first electronic switches and the switchingof the one or more second electronic switches comprise:

-   switching at least one of the one or more first electronic switches    for connecting the first battery to the inverter;-   switching at least one of the one or more second electronic switches    for connecting the second battery to the inverter;-   switching at least one of the one or more first electronic switches    for disconnecting the first battery from the inverter, while    continuing to transform the output current of the second battery to    the alternating output current of the inverter, and then charging    the first battery by a battery charger of the GPU;-   after a certain time switching at least one of the one or more first    electronic switches for connecting again the first battery to the    inverter, in order to transform the output current of the now    recharged first battery to the alternating output current of the    inverter, while blocking or limiting current from the first battery    to the first battery by the second diode.

In a further preferred method of operating a system according to thepresent invention comprising a fourth method of operating a GPU,preferably based on any of the first to third or any of the hereindescribed GPU operation method, the switching of the one or more firstelectronic switches comprise:

-   switching at least one of the one or more first electronic switches    for disconnecting the first battery from the inverter and/or a    charger of the GPU, upon a first battery monitoring device for    monitoring a correct function of the first battery indicates a    malfunction of the first battery; and the switching of the one or    more second electronic switches comprise-   switching at least one of the one or more second electronic switches    for disconnecting the second battery from the in and/or a charger of    the GPU, upon a second battery monitoring device for monitoring a    correct function of the second battery indicates a malfunction of    the second battery.

Preferably, this control scheme is implemented in the centralcontroller.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, whereby

FIG. 1 is a conceptual overview of one embodiment of a GPU according tothe invention,

FIG. 2 is a schematic of the electrical circuit of a preferredembodiment of a GPU according to the invention,

FIG. 3A shows an embodiment of a system for supplying electric currentto an aircraft parked on the ground, based on the embodiment shown inFIG. 2,

FIG. 3B shows and embodiment of a system for supplying electric currentto an aircraft parked on the ground according to the invention,

FIG. 3C shows an embodiment of an input converter for supplying electriccurrent to an aircraft parked on the ground,

FIG. 3D shows an embodiment of an input converter for supplying electriccurrent to an aircraft parked on the ground,

FIG. 4 shows an embodiment of a system for supplying electric current toan aircraft parked on the ground according to the invention,

FIG. 5 shows an embodiment of a system for supplying electric current toan aircraft parked on the ground according to the invention,

FIG. 6A shows an embodiment of a system for supplying electric currentto an aircraft parked on the ground according to the invention,

FIG. 6B shows an embodiment of a system for supplying electric currentto an aircraft parked on the ground according to the invention, and

FIG. 7 shows show an embodiment of a system for supplying electriccurrent to an aircraft parked on the ground according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a conceptual overview of one embodiment of a battery GPUaccording to the invention. It is an airport GPU 1, here mobile onwheels, for supplying electric current to an aircraft parked on theground.

The GPU 1 comprises:

-   a first electric battery 30,-   an inverter 50 for transforming an output of the battery 30 to an    alternating output current of the inverter 50 to be supplied to the    aircraft,-   one first electronic switch 60 for connecting and disconnecting the    first battery 30 to and from the inverter 50, wherein the first    switch 60 is connected in serial to the first battery 30 and wherein    the serially connected first battery 30 and the first switch 60 are    together connected to the inverter 50,-   a first controller unit 10 for controlling the first switch 60.

The GPU 1 further comprises

-   a second electric battery 31 and-   a second electronic switch 61 for connecting and disconnecting the    second battery 31 to and from the inverter 50, wherein the second    switch 61 is connected in serial to the second battery 31 and    wherein the serially connected second battery 31 and the one second    switch 61 are together connected to the inverter 50 such that they    are in parallel to the serially connected first battery 30 and the    first switch 60, wherein the second switch 61 is controlled by the    first digital controller unit, wherein in addition to the first    switch 60 being connected in serial to the first battery 30, a first    diode 70 is connected in serial, allowing current from the first    battery 30 to the inverter 50 and blocking (in case without the    optional first shunt resistor 70.1) or limiting current from the    inverter 50 or the second battery 31 to the first battery 30; and    wherein in addition to the second switch 61 being connected in    serial to the second battery 31, a second diode 71 is connected in    serial, allowing current from the second battery 31 to the inverter    50 and blocking (in case without the optional second shunt resistor    71.1) or limiting current from the inverter 50 or the first battery    30 to the second battery 31.

FIG. 2 shows a schematic of the electrical circuit of a preferredembodiment of as GPU according to the invention, based on the embodimentshown in FIG. 2. In contrast to FIG. 2, there is a second digitalcontroller unit 11 controlling the second switch 61. Furthermore, anadditional first switch 80 and an additional second switch 81 areconnected in serial between the respective battery 30, 31 and theinverter. The first controller 10 controls in addition switch 80 and thesecond controller 11 controls in addition switch 81. Further, in thatsame manner, the GPU 1 comprises a third battery with one or more thirdswitches and third diode and a fourth battery with one or more fourthswitches and fourth diode connected in parallel to the first and secondbattery and respective switches. Features that in the following aredescribed as preferred for the first and second battery scenario, alsoapply (as apparent from the Figure) to the third and fourth batteryscenario/portion.

The diodes are (configured for) completely limiting the current from theinverter or from any other battery than the one to which the diodeconnected to in serial.

The first switch and the second switch are each configured to disconnectboth poles of the respective battery from the inverter.

The GPU comprises a first battery charger configured to charge the firstbattery and a second battery charger configured to charge the secondbattery. The first controller 10 is configured to control the firstcharger 90 and the second controller 11 is configured to control thesecond charger 91. The chargers 90, 91 are connected to one commonconnector 180 of the GPU 1 for connecting the charger to the grid power.

The additional first switch 80 is configured to disconnect the firstbattery 30 from the inverter 50 while not disconnecting the firstbattery charger 90 from the first battery 30 and the additional secondswitch 81 is configured to disconnect the second battery 31 from theinverter 50 while not disconnecting the second battery charger 91 fromthe second battery 31.

The GPU 1 comprises a first battery monitoring device 170 for monitoringa correct function of the first battery 30, wherein the first controller10 is connected to the first battery monitoring device 170 via a firstcommunication line 140 for communication with the first batterymonitoring device 170 and configured to disconnect the first battery 300from the inverter and the charger by opening the first switch, as soonas the first battery monitoring device 170 indicates a malfunction ofthe first battery 30. The GPU 1 comprises a second battery monitoringdevice 171 for monitoring a correct function of the second battery 31,wherein the second controller 11 is connected to the second batterymonitoring device 171 via a second communication line 141 forcommunication with the second battery monitoring device 171 andconfigured to disconnect the second battery 31 from the inverter and thecharger by opening the second switch 61, as soon as the second batterymonitoring device 171 indicates a malfunction of the second battery 31.

The first and second controller 10, 11 each communicate to therespective battery monitoring device via a CAN bus. The firstcommunication line 140 is galvanically isolated from the secondconnection 141 line.

The GPU 1 comprises a digital central controller 110, wherein thecentral controller 110 is connected to a user interface 120, and isconfigured to be controlled by a user using user interface 120, and isconnected to the first controller 10 and to the second controller 11 viaa communication bus 130.

The central controller 110 is configured to send switching to the firstand second controller 10, 11 for connecting or disconnecting and/orcharging the first or second battery 30, 31. The first controller andsecond controller 10, 11 are configured to receive these commands andswitch the one or more first and second switches 60, 61, 80, 81 and orcontrol the first and second chargers 90, 91 accordingly. The centralcontroller 110 is configured to control the inverter 50. Communicationlines of the communication bus 130 between the central controller 11 andthe first and second controller 10, 11 are galvanically insulated fromthe first and second communication lines 140, 141 between the first andsecond controller 10, 11 and the first and second battery monitoringdevice 170, 171.

The first switch 60 and the first battery 30 form a first battery module160 housed in a first housing, and the second switch 61 and the secondbattery 31 form a second battery module 161 housed in a second housing.The battery monitoring devices 170, 171 are also part of the respectiveso formed battery module 160, 161.

The GPU 1 comprises an inductance 100 connected serially between theinverter 50 and the first and second battery 30, 31.

FIG. 3A shows a system for supplying electric current to an aircraftparked on the ground, comprising a battery GPU 1 for supplying electriccurrent to an aircraft parked on the ground, preferably according to oneof the preceding embodiments, the battery GPU 1 comprising one or morebatteries 30, 31, and an inverter 50 for transforming an output currentof the one or more batteries 30, 31 to an alternating output current ofthe inverter 50 to be supplied to the aircraft, wherein the battery GPU1 comprises an alternating current input port 190, wherein the batteryGPU 1 is configured to be connected to an alternating current outputconnector 191′ of a helper GPU 1′ via the alternating current input port190, in order to route an alternating output current of the helper GPU1′ via the alternating current input port 190 to the aircraft. Thealternating current input port 190 comprises an aircraft socket, beingconfigured to be connected to an aircraft output connector 191, 191′adapted to be connected to the aircraft.

The system is configured to synchronize to each other

-   the alternating output current of the inverter 50 of the battery GPU    1 and-   the alternating output current of the helper GPU 1′.

Here, the battery GPU 1 is configured to synchronize itself to thehelper GPU 1′ and to perform a handover of power supply from the one ormore batteries 30, 31 to power delivered by helper GPU 1′.

The battery GPU 1 is configured to shift the phase angle of thealternating output current of the inverter 50. The battery GPU 1,comprises an input coupling switch 200, and the battery GPU 1 isconfigured:

-   to detect a phase angle of the alternating output current of the    helper GPU 1′ and    -   to close the input coupling switch 200, if the difference        between the detected phase angle and a phase angle of the        alternating output current of the inverter 50 of the battery GPU        1 is smaller or equal to a predetermined threshold. The battery        GPU 1, comprises an output decoupling switch 201 and the battery        GPU 1 is configured:-   to open the output decoupling switch 201 if the input coupling    switch 200 has been switched to closed state.

The system is operated as follows:

-   Connecting the helper GPU's 1′ alternating current output connector    191′ to the alternating current input part 190 of the battery GPU 1,    and routing an alternating output current of the helper GPU 1 to the    aircraft via the alternating current input port 190, while the    connecting comprises:-   a) synchronizing, by shifting the phase angle of the alternating    output current of the inverter 50 of the battery GPU 1, to each    other:-   the alternating output current of the inverter 50 of the battery GPU    1, here a phase angle of the output current, and-   the alternating output current of the helper GPU 1′, here a phase    angle of the output current;-   b) detecting a phase angle of the alternating output current of the    helper GPU 1′ and closing the input coupling switch 200, if the    difference between the detected phase angle and a phase angle of the    alternating output current of the inverter 50 of the battery GPU 1    is smaller or equal to a predetermined threshold;-   c) opening the output decoupling switch 201, if the input coupling    switch 200 has been switched to closed state.

FIG. 3B shows a system like the one shown in FIG. 3A. However, insteadof connecting the helper GPU 1′ without voltage/frequencytransformation, the alternating current of the helper GPU 1′ is beingfeed into the DC-bus of the battery GPU 1. The one or more batteries 30,31 are connected to an input port of the inverter 50. The system isconfigured to route the alternating output current of the helper GPU 1′from the alternating current input port 190 via the input port of theinverter 50 to the aircraft. The system comprises an input converter 210which is configured to convert the alternating output current of thehelper GPU 1′ at the alternating current input port 190 to a directedcurrent and to output the directed current to the input port of theinverter 50. Switches 200 and 201 as in FIG. 3A are not necessary.

FIGS. 3C and 3D show different embodiments of the converter 210. Theconvener 210 in FIG. 3C comprises a transformer 211, a 6-pulse rectifier212, a filter 213 using one or more capacitors and a filter diode 214.The filter diode 214 prevents the batteries to feed into the filtercapacitors. The convener 210 in FIG. 3D comprises a choke 215, atransformer 211 and a 12-pulse rectifier 212.

FIG. 4 shows a system like the one shown in FIG. 3A whereas the inputcoupling switch 200′ is implemented in the helper GPU 1′. Furthermore,as an example, helper GPU 1′ is also as battery GPU, preferably abattery GPU with two or more batteries 30′, 31′ according to FIG. 1and/or FIG. 2. In this exemplary hardware setup, one possible operationis the synchronization (by shifting the helper GPU's 1′ inverter 50′phase angle) and switching of input coupling switch 200′ by the helperGPU 1′. Via a communication channel to the battery GPU 1, helper GPU 1′is then switching the decoupling switch 201 to open state. Anotherpossible operation is the synchronization and switching performed by thebattery GPU 1, whereby the information about the helper GPU's 1′inverter 50′ phase angle is sent via a communication channel from thehelper GPU 1′ to the battery GPU 1 and switch 200′ is switched bybattery GPU 1 via a communication channel. As in this setup, there willbe live male pins (=pins under voltage) of the input port 190 duringoperation of the battery GPU 1 when not connected to helper GPU 1′, amechanical protection, e.g. a protection lid, or an additional switchwill need to present for enhancing safety and avoiding users to get intocontact with live male pins. The same is true for the embodimentsaccording to FIGS. 5 and 6A, whereby in FIG. 6A, it is the input port390.2 of the Y-adaptor 300, which may have live male pins and needsprotection.

FIG. 5 shows a system like the one shown in FIG. 4, whereby the outputcable of the battery GPU 1 features the aircraft socket on the inputport 190 by way of a Y-cable configuration.

FIG. 6 shows a system similar to the one shown in FIG. 5, whereby thebattery GPU 1 comprises an Y-adaptor 300 which has two alternatingcurrent input ports 390.1, 390.2 each comprising an aircraft socket andwhich has a an aircraft output connector 391, whereby an aircraft outputconnector 191 of the battery GPU 1 is connected to one of the twoalternating current input ports 390.1. FIG. 6B shows the Y-adaptor 300separately.

FIG. 7 shows a system like the one shown in FIGS. 3A-D, whereby twoidentical GPUs are used for performing a handover from one of the GPUsto the other GPU.

1. A system for supplying electric current to an aircraft parked on theground, comprising a battery ground power unit (1) for supplyingelectric current to an aircraft parked on the ground, the, batteryground power unit (1) comprising one or more batteries (30, 31), and aninverter (50) for transforming an output current of the one or morebatteries (30, 31) to an alternating output current of the inverter (50)to be supplied to the aircraft, wherein the battery ground power unit(1) comprises an alternating current input port (190, 390.2), whereinthe battery ground power unit (1) is configured to be connected to analternating current output connector (191′) of a helper ground powerunit (1′) is the alternating current input port (190, 390.2), in orderto route an alternating output current of the helper ground power unit(1′) via the alternating current input port (190, 390.2) to theaircraft.
 2. The system according to claim 1, wherein the alternatingcurrent input port (190, 390.2) comprises an aircraft socket, beingconfigured to be connected to an aircraft output connector (191, 191′)adapted to be connected to the aircraft.
 3. The system according toclaim 2, whereby the battery ground power unit (1) comprises anY-adaptor (300) which has two alternating current input ports (390.1,390.2) each comprising an aircraft socket and which has a an aircraftoutput connector (391), whereby an aircraft output connector (191) ofthe battery ground power unit (1) is connected to one of the twoalternating current input ports (390.1).
 4. The system according toclaim 1, wherein the system is configured to synchronize to each other:the alternating output current of the inverter (50) of the batteryground power unit (1) and the alternating output current of the helperground power unit (1′).
 5. The system according to claim 4, whereby thesystem comprises an input coupling switch (200, 200′), and whereby thesystem is configured to detect a parameter of the alternating outputcurrent of the helper ground power unit (1′) and to close the inputcoupling switch (200, 200′), if the difference between the detectedparameter and a respective parameter of the alternating output currentof the inverter (50) of the battery ground power unit (1) is smaller orequal to a predetermined threshold.
 6. The system according to claim 4,wherein the system is configured to shift a parameter of the alternatingoutput current of the inverter (50) of the battery around power unit (1)and/or to shift a parameter of the alternating output current of thehelper ground power unit (1′).
 7. The system according to claim 6,whereby the system comprises an output decoupling switch (201), andwhereby the system is configured to open the output decoupling switch(201), if the input coupling switch (200, 200′) has been switched toclosed state.
 8. The system according to claim 7, whereby the systemfurther comprises the helper ground power unit (1′), whereby the batteryground power unit (1) and the helper ground power nun (1′) are connectedto each other via the alternating current input port (190) of thebattery ground power unit (1) and the alternating current outputconnector (191′) of the helper ground power unit (1′).
 9. The systemaccording to claim 8, whereby for transforming the output current of theone or more batteries (30, 31) to the alternating output current of theinverter (50), the one or more batteries (30, 31) are connected to aninput port of the inverter (50), and whereby the system is configured toroute the alternating output current of the helper ground power unit(1′) from the alternating current input port (190) via the input port ofthe inverter (50) to the aircraft and wherein the system comprises aninput converter (210) which is configured to convert the alternatingoutput current of the helper ground power unit (1′) at the alternatingcurrent input port (190) to a directed current and to output thedirected current to the input port of the inverter (50).
 10. The systemaccording to claim 9, wherein the input converter (210) comprises one ormore of transformer (211), rectifier (212), filter (213), filter diode(214), choke (215).
 11. The system according to claim 3, wherein theY-adaptor (300) has two alternating current input ports (390.1, 390.2)each comprising an aircraft socket, and which has an aircraft outputconnector (391).
 12. A method of operating a system for supplyingelectric current to an aircraft parked on the ground, comprising abattery ground power unit (1) for supplying electric current to anaircraft parked on the ground, preferably according to one of the GPUembodiments described in this application, by using one or morebatteries (30, 31), preferably using a GPU control method according toone of the GPU control methods described in this application, and thesystem further comprising a helper ground power unit (1′) for supplyingelectric current to an aircraft parked on the ground, wherein the methodcomprises the steps of: connecting a helper ground power unit's (1′)alternating current output connector (191′) to an alternating currentinput port (190, 390.2) of the battery ground power unit (1), androuting an alternating output current of the helper ground power unit(1′) to the aircraft via the alternating current input port (190,390.2).
 13. The method according to claim 12, whereby the connectingcomprises one or more of the following steps a)-c); a) synchronizing toeach other the alternating output current of the inverter (50) of thebattery ground power unit (1) and the alternating output current of thehelper ground power unit (1′); b) detecting a parameter of thealternating output current of the helper ground power unit (1′) andclosing an input coupling switch (200, 200′), if the difference betweenthe detected parameter and a respective parameter of the alternatingoutput current of the inverter (50) of the battery ground power unit (1)is smaller or equal to a predetermined threshold; and preferably c)opening output decoupling switch (201), if the input coupling switch(200, 200′) has been switched to closed state.
 14. The method accordingto claim 12, whereby the alternating output current of the helper groundpower unit (1′) is routed from the alternating current input port (190)via an input port of the inverter (50) to the aircraft.